Question

所以这个程序应该计算一行结果矩阵。但我的代码并没有做到它应该做的事情。

#include <iostream>
#include <fstream>
#include <pthread.h>
#include <ctime>
#include <regex>
using namespace std;

//matrix A and B, result will be store as matrix C
int A[10000][10000], B[10000][10000], C[10000][10000];
int rowFirst, columnFirst, rowSecond, columnSecond;
int numThread;

struct threadLine {
int tid;
int lineNum;
int rowFirst;
int rowSecond;
int columnFirst;
int columnSecond;
};

//function to multiply matrix A and B
void* matrix (void* lineNumber)
{
    int i, j, k;
    int line = (long)lineNumber;

    // Multiplying matrix A and B and store it in matrix C.
    // per row
    //for(i = 0; i < line; ++i)
    //{
        for(j = 0; j < columnSecond; ++j)
        {
            C[i][j] = 0;
            for(k = 0; k < columnFirst; ++k)
            {
                C[i][j] += A[line][k] * B[k][j];
            }
        //C[i][j] = temp;
        }
    //}

   return 0;
   }

   int main()
   {

//read the file called matrix
ifstream read("matrix.txt");

// if it can read
if (read)
{
    read >> rowFirst >> columnFirst;                //read the first matrix

    //thread ids
    pthread_t tid[rowFirst];
    struct threadLine tl[rowFirst];

    for (int i = 0; i < rowFirst; i++)
    {
        for(int j = 0; j < columnFirst; j++)
        {
            read >>A[i][j];                         //store it in array A
        }
    }
    read >> rowSecond >> columnSecond;              //read the second matrix

    if (columnFirst != rowSecond)                   //column of first matrix must be the same as the second one
    {
        cout << "column of first matrix must have the same value as row of second matrix" << endl;
        return -1;
    }

    else
    {
        for (int i = 0; i < rowSecond; i++)
        {
            for(int j = 0; j < columnSecond; j++)
            {
                read >>B[i][j];                         //store it in array B
            }
        }

        //print input data
        cout << "Matrix A: ";                           //print array A
        for (int i = 0; i < rowFirst; i++)
        {
            for(int j = 0; j < columnFirst; j++)
            {
                cout << A[i][j] << ' ';
            }
            cout << endl;
        }

        cout << "Matrix B: ";                           //print array B
        for (int i = 0; i < rowSecond; i++)
        {
            for(int j = 0; j < columnSecond; j++)
            {
                cout << B[i][j] << ' ';
            }
            cout << endl;
        }
        cout << endl;

        int timeStart = clock();                        //start time counting

        //loop for creating threads based on number of row (calculate per row)
        for (int x = 0; x < rowFirst; x++)
        {

            int idSuccess = pthread_create(&tid[x], NULL, matrix, (void *) x);
            cout << "Created worker thread " << tid[x] << " for row " << x << endl;

            //check to see if thread is created sucessfully
            if (idSuccess)
            {
                cout << "Thread creation failed : " << strerror(idSuccess);
                return idSuccess;
            }
        }
        cout << endl;

        //wait for every threads complete
        for (int x = 0; x < rowFirst; x++)
        {
            pthread_join(tid[x], NULL);
        }

        int timeStop = clock();                         //stop time counting

        cout << "Matrix C = A x B: ";                   //display result
        for (int i = 0; i < rowFirst; i++)
        {
            for(int j = 0; j < columnSecond; j++)
            {
                cout << C[i][j] << " ";
                if(j == columnSecond - 1)
                {
                    cout << endl;
                }
            }
        }

        cout << endl;

        //print out time
        double timeVal = (timeStop -
       timeStart)/double(CLOCKS_PER_SEC)*1000;
        cout << "Total execution time using " << numThread << " threads is " << timeVal << " ms."<< endl;

    }


}
else if(!read)
{
    cout << "Unable to read file" << endl;
}

}

我原以为输出会是这样的：矩阵C = A x B：3 17 10 11

2 -10 -6 -7

16 11 5 -5

4 52 30 27

相反，我得到了这个：

矩阵C = A x B：4 52 30 27

0 0 0 0

它只计算第一行。我不确定原因是什么。

Pthreads创建无法正常工作

0 个答案: